Denzel E. Ferguson

Newts: Sun-Compass Orientation

Rough-skinned newts, captured from breeding ponds, oriented on courses that would have intersected the familiar shorelines at right angles, when released in a circular arena on land under the sun or moon. Pondward migrants oriented similarly. Reorientation failed under complete cloud cover and after 7 days of darkness in an environmental chamber, but persisted in newts whose eyes were excised and in those displaced more than 27 kilometers in darkness. Both normal and blind animals compensated for displacement in sunshine. Preliminary evidence suggests that alternative light receptors in blinded animals may be associated with the optic tectum. No evidence of olfactory guidance was observed.

Extraoptic Celestial Orientation in the Southern Cricket Frog Acris gryllus

Celestial orientation and setting of the biological clock in the southern cricket frog Acris gryllus can be cued by light stimuli received by extraoptic receptors in the brain. These extraoptic photoreceptors may also be used in learning new orientational directions. A mechanism for a light-activated biological clock is discussed.

Sun compass orientation of the northern cricket frog, Acris crepitans

Summary When released in water at the centre of a circular pen 50 ft in diameter, northern cricket frogs ( Acris crepitans ) from shores of natural bodies of water oriented on a compass course (Y-axis) that bisected the home shore at rightangles. Frogs taken to the test pen in closed containers responded similarly to those moved in view of the sky, and Y-axis orientation was unaffected in individuals displaced 115 miles east in light-tight containers. Specimens from opposite shores oriented to their respective Y-axis, even when released simultaneously. When a large number of individuals was collected from one segment of shore line and held in darkness for periodic release during a 24-hr period, orientation persisted under the sun, moon, and/or stars. Cricket frogs held in darkness at a constant temperature for periods of 30 hr and up to 7 days exhibited a decline in accuracy of Y-axis orientation that culminated in a random pattern after 7 days. Apparently differences in phase synchronization between the frogs timing mechanism and local time were responsible for the failure to orient. Orientation was reestablished to the original Y-axis by exposing ‘dephased’ specimens to the normal light-dark regime or to daily temperature and humidity fluctuations. A photo-period of normal duration, but administered 6 hr early (or late) relative to local time, reestablished orientation, but on a Y-axis 90° to the left (or right) of the original. A daily exposure to 10 min indirect light was sufficient to reestablish orientation in 8 days. A learned shore position, view of a useful celestial cue, and a timing mechanism phased to local time are necessary for Y-axis type of orientation. The demonstrated use of several types of temporal cues in the cricket frog suggests that alternative sources of information from several environmental components may be employed in nature, depending upon circumstance and availability. Y-axis type of orientation is a complex mechanism and appears to be a basic behavioural characteristic shared by most or all anurans

Dynamics of Endrin Uptake and Release by Resistant and Susceptible Strains of Mosquitofish

Abstract Results of bioassays and gas chromatographic analyses show that mosquitofish, Gambusia affinis, from near heavily-treated cotton fields near Belzoni, Mississippi (36-hr TLm = 1,000 ppb) and from an uncontaminated site near State College, Mississippi (36-hr TLm = 1 ppb) remove endrin from static test solutions at the same rate. A 500 ppb endrin solution produced 32% mortality in 50 susceptible fish in 25 min but required 144 hr in resistant fish. Relative mortality of fed and starved fish in endrin solutions and the rate of endrin uptake discount swallowing as the primary pathway of endrin entry into mosquitofish. About six times as much endrin is taken up via the exposed head region as is taken up by the general body surfaces. Oxygen requirements of the two populations are similar, but increase for susceptible fish at low endrin concentrations and for resistant fish at high concentrations coincident with the appearance of symptoms of endrin poisoning. Both bioassays and residue analyses revealed ...

Resistance to DDT in the Mosquito Fish, Gambusia affinis

Mosquito fish from waters near cotton fields that have had a long history of treatment with chlorinated hydrocarbon pesticides exhibited a marked resistance to DDT compared with fish from areas which had had no past exposure to insecticides.

Celestial Orientation of Fowler's Toad b uFo Fowleri

Young Fowlers toads from on and near the shores of a lake were tested in a circular pen 60 feet in diameter. Under a variety of conditions (e.g. including group tests, individual tests, simultaneous testing of two groups from different shores, long distance displacement, and transit to the test pen both in view of the sky and in lightproof containers), the toads oriented under the sun to a compass direction (Y-axis) corresponding to a line bisecting the home shoreline at right angles. This orientation persisted after 72 hours in darkness, indicating the existence of an internal clock mechanism. Reorientation to a new shore was evident in 24 hours and was virtually complete after 48 hours. Orientation failed or was partially inhibited in small toads tested under dense cloud cover, at noon, and after sunset. Also, the type of orientation exhibited under the sun was evident at night under the moon, but to a lesser extent under starry skies. These mechanisms are useful in foraging and in dispersal from nursery shores. Adults are oriented at night to the breeding site even without benefit of a chorus for reference. Adults oriented to the Y-axis of the breeding site. A recorded chorus distracted migrating adults pursuing a compass course toward a pond. Non-breeding adults compensated for a displacement made in view of the sun. Celestial orientation is considered a basic orientational mechanism which most likely developed early in anuran history.

Sources of error in the use of fish-brain acetylcholestrinase activity as a monitor for pollution

Recurring pollution of natural waters from the manufacture s~ud use of pesticides has accentuated the need for suitable monitoring methods. The determination of fish-brain acetylcholinesterase (ACHE) activity has been proposed as a means of detecting organophosphorous pollution (4) and has been used for monitoring purposes (5, 6). Weiss (1, 2, 3) demonstrated that a 40-7~ inhibition of fish-brain AChE is usually lethal. He detected inhibition from concentrations of phosphate insecticides as low as 1 ppb over a 15 day exposure period and Ool ppb over a 30 day exposure period. Williams and Sova (5) detected inhibition in brains of two SPecies of fishes collected downstream from suspected sources of organophosphorous pollution. Holland et al. (6) evaluated this monitoring method and reported AChE inhibition in fish from polluted waters. AChE inhibition data have been used as evidence implicating agricultural chemical plants in

Possible DDT Resistance in Two Species of Frogs

Possible resistance to DDT is demonstrated in natural populations of cricket frogs (Acris crepitans and A. gryllus). Frogs, classed according to snout-vent length, were tested from several Mississippi localities by exposure to different DDT concentrations for 36 hr. Mortality data for the two species from heavily treated cotton fields and untreated areas were generally lower in populations having a history of exposure to DDT. Field observations following treatment are described where the selective pressures appeared sufficient to have forced expression of resistant genotypes if present in the population.

Sun-Compass Orientation of Bullfrogs

Orientational responses of bullfrogs (Rana catesbeiana) were determined on land in a circular arena (50 ft diameter, 6 ft height). During the spring, field-collected frogs used celestial cues to orient on the compass course that intersects the home shoreline at right angles (Yaxis). Bullfrogs exhibited oriented behavior in both daytime and nighttime tests, but not under complete cloud cover. Orientation on the Y-axis ceased in summer tests, but reappeared in the fall. Bullfrogs caged on various natural shores oriented to the Y-axes of their new surroundings in the spring, but failed to do so during the summer. Frogs in captivity and in tests exhibited seasonal variations in behavior that seemed correlated to seasonal changes in Y-axis response. Individuals kept in pens with small artificial pools at one end oriented in the direction of the pools in tests. Although frogs normally moved toward water on the Y-axis, subadults moved in an opposite direction when tested at night.

Newt Orientation by Sun-compass

SALAMANDERS migrate long distances to breeding sites1, and apparently possess an accurate guidance mechanism2,3. The homing of blinded Taricha after being displaced downstream suggests that they rely on olfactory cues4. The ability of the normal animal to use vision in orientation, however, has received little attention. Three species of frogs and toads use a sun-compass5–7, and the toad, Bufo woodhousei fowleri, can learn a direction of escape relative to a light cue8.